The present invention relates to a bracket suspended from a hanger on the outermost beam of a bridge deck. The bracket is necessary for the support of formwork and steel and poured-in-place concrete until the concrete has cured and will support itself. The bracket is then removed for use elsewhere.
The prior art has numerous methods of temporarily supporting the concrete in the plastic state. Several well known methods employ metal hangers straddled to the top flange of the beams and connected to forms by bolts or other connectors. One common method is referred to as the needlebeam and consists of a structural steel or timber beam hung from the bottom flange of the outside beam, extending out under the overhanging slab and under the adjacent interior beam for reaction. A jack is provided to support and adjust the form from this fixed position beam. This method requires substantial scaffolding for installation and removal, the tall jacking means and the necessity to work from underneath to adjust the form.
The most popular prior art method is the use of the structural steel bracket that is suspended by means of a bolt, usually at a 45.degree. angle, from a hanger anchored to or installed to straddle the top flange of the exterior beam. U.S. Pat. Nos. 3,755,983; 3,782,674; 3,806,074; and 3,981,469 all reveal the use of such a structure. The brackets currently commercially available all make use of this type of suspension. The compression support member is adjustable along with means for vertically adjusting the height of the bracket. Yet, there are disadvantages to using this bracket. When a superimposed load is applied at the heel of the bracket close to the beam, the bolt tends to swing toward the vertical and when a load is applied near the distal end of the bracket, the bolt tends to swing toward the horizontal. In either case, the entire bracket obviously shifts from its adjusted position in a "rocking chair" effect, making calculation of its carrying capacity indeterminant.
This rocking chair effect is particularly troublesome when the state of the art concrete slab placement equipment is used. Generally two machines are used, a concrete distributor and a concrete finisher. When these machines are put to use across the brackets themselves, the brackets must support extremely high loads for a short period of time as the distributor or the finisher machines roll across them. Since the machines must, if full advantage of the machine's function is to be realized, be supported outside the extreme portion of the concrete, the load imposed by these machines creates the objectional "rocking chair" effect making the results of the pour unacceptable.
The present invention retains the advantages of existing art since the bracket can be installed and completely adjusted by workman working from the top of the beams and formwork without the use of scaffolding and can be removed by use of a simple scaffold suspended from the completed bridge, while eliminating the rocking chair effect, and making calculation of carrying capacity determinant and finite. The present invention provides for the full efficient use of the state of the art concrete slab placement equipment and provides adjustment features not present in any prior art form support brackets.
Generally, it is an object of the invention to provide a statically determinant support bracket for the formwork, steel and concrete while in the plastic state and through the curing period of the concrete installed on bridge and deck overhangs.
A more specific object of the invention is to provide a hanger and bracket joined through a substantially vertical connection which assumes vertical load and horizontal loads without experiencing the rocking effect associated with prior art hangers.
It is a further object of the invention to provide a support bracket which is adjustable as to both elevation and slope relative to the beam to which it is attached.
It is a further object of the invention to eliminate the need for scaffolding in the installation of the bracket in that all installation, adjustment, and final placement of the bracket is performed by workmen from the top of the bridge beam.
It is another object of the invention to provide a bracket which does not require any jacking or support means from the ground or from a structure other than the bridge beam to which it is attached.
It is another object of the invention to provide a bracket which can be folded and easily stored, handled and transported to and from job sites.
It is another object of the invention to provide an equipment rail mounting device which is adjustable both vertically and horizontally and which can not be positioned so as to not cause the torque or bending moment resulting from the superimposed load upon the rail mounting device to overload the bracket or bridge beam.